feat(kv): add put_not_exists and compare_and_swap transactions

shard.yml

@@ -1,5 +1,5 @@
 name: etcd
-version: 0.1.0
+version: 0.2.0
 
 authors:
   - Caspian Baska <[email protected]>
@@ -14,5 +14,5 @@ development_dependencies:
     github: crystal-ameba/ameba
     version: ~> 0.10.1
 
-crystal: 0.30.1
+crystal: 0.32.0
 license: MIT

spec/kv_spec.cr

@@ -1,16 +1,18 @@
+require "uuid"
 require "./helper"
 
 module Etcd
   describe Kv do
-    pending "compare_and_swap" do
+    describe "compare_and_swap" do
       it "puts if compare succeeds" do
         client = Etcd.from_env
         key = "#{TEST_PREFIX}/hello"
         value0 = "world"
         value1 = "friends"
         client.kv.put(key, value0)
-        response = client.kv.compare_and_swap(key, value: value1, previous_value: value0)
-        pp! response
+        success = client.kv.compare_and_swap(key, value: value1, previous_value: value0)
+        success.should be_true
+        client.kv.get(key).should eq value1
       end
 
       it "fails if compare fails" do
@@ -19,8 +21,32 @@ module Etcd
         value0 = "world"
         value1 = "friends"
         client.kv.put(key, value0)
-        response = client.kv.compare_and_swap(key, value: value1, previous_value: "ginger nut")
-        pp! response
+        success = client.kv.compare_and_swap(key, value: value1, previous_value: "ginger nut")
+        success.should be_false
+        client.kv.get(key).should eq value0
+      end
+    end
+
+    describe "put_not_exists" do
+      it "succeeds if no key present" do
+        client = Etcd.from_env
+        lease = client.lease.grant 5
+        key = "#{TEST_PREFIX}/#{UUID.random}"
+        value = "hello world"
+        success = client.kv.put_not_exists(key, value: value, lease: lease[:id])
+        success.should be_true
+        client.kv.get(key).should eq value
+      end
+
+      it "fails if a key is present" do
+        client = Etcd.from_env
+        key = "#{TEST_PREFIX}/#{UUID.random}"
+        value0 = "hello world"
+        value1 = "bye world"
+        client.kv.put(key, value: value0)
+        success = client.kv.put_not_exists(key, value: value1)
+        success.should be_false
+        client.kv.get(key).should eq value0
       end
     end
 

src/etcd/api.cr

@@ -51,8 +51,10 @@ class Etcd::Api
       value.transform_values { |v| to_stringly(v) }
     when NamedTuple
       to_stringly(value.to_h)
-    when String, Bool
-      value
+    when String
+      value.as(String)
+    when Bool
+      value.as(Bool)
     else
       value.to_s
     end

src/etcd/kv.cr

@@ -96,8 +96,40 @@ class Etcd::Kv
   # Non-Standard Requests
   ##############################################################################
 
-  def compare_and_swap(key, value, previous_value)
-    key, value, previous_value = {key, value, previous_value}.map &->Base64.strict_encode(String)
+  # Sets a key if the key is not already present.
+  #
+  # Wrapper over the etcd transaction API.
+  def put_not_exists(key : String, value, lease : Int64 = 0_i64) : Bool
+    key = Base64.strict_encode(key)
+    value = Base64.strict_encode(value.to_s)
+    post_body = {
+      :compare => [{
+        :key    => key,
+        :value  => Base64.strict_encode("0"),
+        :target => "VERSION",
+        :result => "EQUAL",
+      }],
+      :success => [{
+        :request_put => {
+          :key          => key,
+          :value        => value,
+          :lease        => lease,
+          :ignore_lease => false,
+        },
+      }],
+    }
+
+    response = client.api.post("/kv/txn", post_body)
+    Model::TxnResponse.from_json(response.body).succeeded
+  end
+
+  # Sets a `key` if the given `previous_value` matches the existing value for `key`
+  #
+  # Wrapper over the etcd transaction API.
+  def compare_and_swap(key, value, previous_value) : Bool
+    key = Base64.strict_encode(key)
+    value = Base64.strict_encode(value.to_s)
+    previous_value = Base64.strict_encode(previous_value.to_s)
     post_body = {
       :compare => [{
         :key    => key,
@@ -113,10 +145,8 @@ class Etcd::Kv
       }],
     }
 
-    puts post_body.to_json
-    response = client.api.post("/kv/txn", post_body.to_json)
-
-    response
+    response = client.api.post("/kv/txn", post_body)
+    Model::TxnResponse.from_json(response.body).succeeded
   end
 
   def get(key) : String?

src/etcd/model/kv.cr

@@ -34,4 +34,10 @@ module Etcd::Model
     getter deleted : Int32?
     getter prev_kvs : Array(Kv)?
   end
+
+  class TxnResponse < Base
+    getter header : Header
+    getter succeeded : Bool = false
+    getter responses : Array(JSON::Any) = [] of JSON::Any
+  end
 end